1. Field of the Invention
The present disclosure generally relates to methods of treating process water using a reactor for generating chlorine dioxide onsite.
2. Description of the Related Art
With the decline of gaseous chlorine as a microbiocide, various alternatives have been explored; including bleach, bleach with bromide, bromo-chloro dimethylhydantoin, ozone, and chlorine dioxide (ClO2). Of these, chlorine dioxide has generated a great deal of interest for control of microbiological growth in a number of different industries, including the dairy industry, the beverage industry, the pulp and paper industry, the fruit and vegetable processing industries, various canning plants, the poultry industry, the beef processing industry and miscellaneous other food processing applications. Chlorine dioxide is also seeing increased use in municipal potable water treatment facilities and in industrial waste treatment facilities, because of its selectivity towards specific environmentally-objectionable waste materials, including phenols, sulfides, cyanides, thiosulfates, and mercaptans. In addition, chlorine dioxide is being used in the oil and gas industry for downhole applications as a well stimulation enhancement additive.
Unlike chlorine, chlorine dioxide remains a gas when dissolved in aqueous solutions and does not ionize to form weak acids. This property is at least partly responsible for the biocidal effectiveness of chlorine dioxide over a wide pH range. Moreover, chlorine dioxide is a highly effective microbiocide at concentrations as low as 0.1 parts per million (ppm) over a wide pH range.
The biocidal activity of chlorine dioxide is believed to be due to its ability to penetrate bacterial cell walls and react with essential amino acids within the cell cytoplasm to disrupt cell metabolism. This mechanism is more efficient than other oxidizers that “burn” on contact and is highly effective against legionella, algae and amoebal cysts, giardia cysts, coliforms, salmonella, shigella, and cryptosporidium. 
Unfortunately, chlorine dioxide in solution is unstable with an extremely short shelf life and thus, is not commercially available. Chlorine dioxide solutions must typically be generated at its point of use such as, for example, by a reaction between a metal chlorate or metal chlorite in aqueous solution and a liquid phase strong acid. However, the use of liquid phase strong acids poses handling issues and safety concerns.
Production of chlorine dioxide using chlorate, hydrogen peroxide, acid generates heat and may result in inadvertent explosive decomposition of chlorine dioxide if the temperature is not properly controlled.